Area Forecast Discussion
Issued by NWS Jackson, KY

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814 FXUS63 KJKL 190546 AFDJKL AREA FORECAST DISCUSSION National Weather Service Jackson KY 146 AM EDT Tue Sep 19 2017 .UPDATE... Issued at 146 AM EDT TUE SEP 19 2017 Did a update to freshen up the short term grids. No significant changes. GOES-16 showing another night of valley fog, but a bit more mid level clouds moving in tonight, which could limit it a bit more than the previous nights. We could still see some locally dense fog however. UPDATE Issued at 1045 PM EDT MON SEP 18 2017 Freshened up the near term grids to make sure they were on track with the latest observations. Several locations in the far eastern portion of the CWA have dropped near to or even below the forecasted lows for overnight. This led to some adjustments in the overnight lows and diurnal trends to better accommodate the current trends. Also, the HWO and TAFs are giving dense fog wording, but noticed it was not reflected in the grids. Went ahead and added dense fog after 6Z, ranging from patchy to areas. All changes have been published and sent to NDFD/web. A new forecast package was sent out to reflect these changes and change to overnight wording. UPDATE Issued at 755 PM EDT MON SEP 18 2017 Forecast is on track so far this evening. Loaded in the latest observations to make sure the near term grids were on track with current conditions. Still a few isolated showers ongoing across the far western portion of the CWA. Once these have tapered off, will update the grids to remove the pre-first period rain mention and sent out a new forecast package. All changes have been published and sent to NDFD/web. && .SHORT TERM...(This evening through Tuesday night) Issued at 435 PM EDT MON SEP 18 2017 20z sfc analysis shows weak high pressure in place over eastern Kentucky though it is not effective in suppressing a few showers now popping up over western parts of the Cumberland Valley. On satellite, most of the area is seeing just small patches of cu, but through the breadth of the Cumberland Valley, where the showers are active, the clouds are more extensive and robust. Plenty of sunshine for most of the area have sent temperatures up into the lower 80s. Meanwhile, dewpoints are holding in the low to mid 60s with the winds still light and variable. The models are in fairly good agreement with the recent changes in the mid and upper air patterns through the short term portion of the forecast. They all now are a bit more hearty with the energy that initially drifts through the weakening ridge this evening and then even more so on Tuesday afternoon and evening. This latter batch will lower heights and pool like a small trough between periods of still rather weak ridging into Wednesday morning. Given this agreement have favored a blended model solution along with a good portion of specifics from the higher resolution HRRR and NAM12 and a healthy dose of persistence - especially tonight and early Tuesday morning. Sensible weather will feature some widely scattered showers through early evening - mainly over the western parts of the CWA. a stray thunderstorm cannot be ruled out, as well. Otherwise, it will be more of the same with clearing skies this evening and cooling conditions leading to areas of fog - locally dense in the river valleys for Tuesday morning. Look for the fog to dissipate a bit quicker Tuesday morning as clouds move in from the west ahead of a weak front. This will likely result in showers and thunderstorms developing by early afternoon favoring the western portion of the forecast area. The convection will die out in the evening setting the stage for more fog development that night into Wednesday morning - though limited by more clouds being around through the night. The CONSShort and ShortBlend were used as the starting point of all the grids. Did make some adjustments to the temperature ones each night based on terrain in anticipation of small to moderate ridge/valley splits. As for PoPs, did tweak them for the diurnal cycle peaking late afternoon and diminishing after sunset. .LONG TERM...(Wednesday through Monday) Issued at 306 PM EDT MON SEP 18 2017 An upper level ridge will amplify over the Ohio Valley through the period continuing the unseasonably warm weather pattern for our area. A weak upper trough trapped between Hurricane Jose and the building ridge over the Mississippi Valley will cause the potential for a few showers and storms Wednesday and Thursday. That potential shifts to our southwest and withers as the upper trough dissolves and surface high pressure builds southward ensuring a dry weekend for our region. Temperatures are expected to consistently top out in the low to mid 80s each day through the period. Overnight lows are forecast in the low 60s, then dropping into the upper 50s over the weekend as drier air filters in. && .AVIATION...(For the 06Z TAFS through 06Z Tuesday night) ISSUED AT 146 AM EDT TUE SEP 19 2017 Another complex night of valley fog and unlike the past few nights, we do have some mid level clouds approaching the area and could act to limit the fog density tonight. Dewpoints are also running lower in the east and higher in the west than the past few nights, so current thinking is the fog will be more suppressed into the eastern valleys tonight, and perhaps a little more broad, but not as dense in the west. This will still have potential to impact the TAF sites with some reductions expected at KSME and KLOZ. Fog will burn off a bit quicker in the morning with most fog gone by 9 am. This will allow a return to VFR conditions. A few widely isolated storms are possible Tuesday afternoon, but confidence in the coverage is not high enough to include in the TAFs at this time. && .JKL WATCHES/WARNINGS/ADVISORIES... NONE. && $$ UPDATE...KAS SHORT TERM...GREIF LONG TERM...ABE AVIATION...KAS

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